The present invention relates to a new and improved construction of control apparatus for use in a gas dynamic pressure-wave machine for charging combustion engines.
Generally speaking, with the control apparatus for a gas dynamic pressure-wave machine as contemplated by the invention, the high-pressure exhaust gas channel of the pressure-wave machine is provided at a location forwardly where it opens into the housing of the cell rotor with a gas pocket for branching-off high-pressure exhaust gases into a shunt or auxiliary flow at certain operating conditions of the engine.
In order to improve the scavenging or flushing of a gas dynamic pressure-wave machine of a charged combustion engine in the idle temperature range below 300.degree. C. there are used gas pockets into which there is branched-off part of the high-pressure exhaust gas which enters the pressure-wave machine, whereas the remaining part of the high-pressure exhaust gas directly enters into the cells of the rotor and performs the actual compression work. With such design the part of the high-pressure exhaust gas which produces the compression work generates, at full load operation of the engine, the charging or boost pressure needed therefor.
On the other hand, if a pressure-wave machine, for instance employed in conjunction with passenger vehicles, is optimumly designed for low full load rotational speeds, then at high full load rotational speeds it delivers too high charging pressures, Hence, with such applications the inflow to the gas pocket in the idle temperature range must be open in order to improve scavenging and also in the temperature range of the high full load rotational speed in order to reduce the too high charging pressure, whereas such inflow or infeed must be closed in the temperature range of the low full load rotational speeds.
Therefore, in order to obtain a satisfactory accommodation of the delivery characteristic for the combustion air it is necessary to control the gas pocket inflow in accordance with what has been previously explained.
A heretofore known solution which proceeds in this direction, as disclosed in Swiss Pat. No. 330,610, contemplates either diminishing the excessive charging or boost pressure or the flow of the high-pressure exhaust gas which is conducted through the pressure-wave machine by using an excess pressure relief device, for instance an automatically opening flap valve. The excess charging air is then exhausted into the surroundings or a part of the high-pressure exhaust gas, prior to entry into the pressure-wave machine, is delivered by an auxiliary or shunt line directly into the low-pressure exhaust gas line, i.e., is infed to the exhaust gas line and thus delivered to the surroundings or ambient atmosphere.
These heretofore known measures for the accommodation of the delivery characteristic of a pressure-wave machine to the momentary air requirements of the engine are however unsatisfactory as concerns their mode of operation, since they do not allow for any continuous control of the gas or air flow, as the case may be. They open and close at predetermined pressures, and furthermore there possibly occurs a certain accommodation of the throughflow by performing a velocity and cross-sectional area dependent throttling by the action of the flap member or valve. Importantly, they fail to take into account the temperature which likewise must be employed as a control parameter in order to obtain an optimum operating behavior of the engine. Apart from the foregoining there is also to be mentioned that the energy of the exhausted charging or boost air and the gase which outflows through the exhaust manifold is lost for energy balancing the assembly or unit and also for scavenging in the cell rotor.
From the standpoint of the operational security or integrity of the system there is also to be mentioned that the described exhaust or auxiliary flow devices are subjected to pronounced wear by the action of the high temperatures and the frequent actuation of their components or parts, such as bolts, springs, levers and the like, and due to the carbon or soot present in the exhaust gases also experience a decisive contamination, and hence, are correspondingly prone to malfunction or disturbance.